Developing device for an electrostatic recording apparatus



Oct. 14,1969 TA lTSUCHgYA ETAL 3,472,205

DEVELOPING DEVICE FOR AN ELECTROSTATIC RECORDING APPARATUS Filed Jun 21, 1966 2 Sheets-Shet 1 27 Egg-5 1 l I v ,INVEXTOR:

26 fi E TSUCH/YA ETAL.

Oct. 14, 1969 TAKEsHl s c w ET AL 3,472,205

DEVELOPING DEVICE FOR AN ELECTROSTA'IiC RECORDING APPARATUS Filed June 21, 1966 2 Sheets-Sheet 2 FIG. 3

VOLTAGE ADJUSTER United States Patent DEVELOPING DEVICE FOR AN ELECTROSTATIC RECORDING APPARATUS Takeshi Tsuchiya, Tokyo, Tetsuo Takahaslii, Kawasakishi, Kiyoshi Yamamoto, Yokohama-shi, and Akito Yanai, Mikio Takiura, and Toshio Kano, Tokyo, Japan, assignors to Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Japan, a corporation of Japan Filed June 21, 1966, Ser. No. 559,141 Claims priority, application Japan, June 25, 1965, 40/51,856; July 10, 1965, 40/41,374; July 24, 1965, 40/60,819; July 31, 1965, 40/62,685

Int. Cl. B05b 5/02 US. Cl. 118-637 5 Claims ABSTRACT OF THE DISCLOSURE A developing device for an electrostatic recording apparatus wherein a supplementary developing agent contained within a supplementary vessel is transferred to the main developing vessel by means of a rotating magnetic brush mounted in the supplementary vessel which supplies the supplementary developing agent to a conveying means which is maintained at a voltage having a polarity opposite to that of the charge of the supplementary developing powder to attract the supplementary developing powder. Scraping means is provided for removing the supplementary developing powder from the conveying means, and removed powder falling into the main developing vessel to supplement the developing powder therein.

This invention relates to a multi-electrode type electrostatic recording device and more particularly to improvements in the relating to an electrode member for recording electrostatic latent images and developing means for converting electrostatic latent images into visible powder images.

As is well known in the art, in electrostatic facsimiles wherein received signals are reproduced by electrostatic printing technique the recording electrode member adapted to form electrostatic latent images on a recording medium generally comprises an electric insulator made of synthetic resin, for example, and a plurality of needle electrodes embedded in said insulator along a straight line. In order to sequentially apply the voltage for forming the electrostatic image upon respective needle electrodes a signal voltage distributor is utilized comprising a plurality of stationary annular distributing electrodes of the number corresponding to that of the needle electrodes and rotary electrodes or brushes sliding on respective distributing electrodes.

Thus, received input signals are impressed upon the rotary electrodes of the signal voltage distributor, and the signal voltage is sequentially applied to respective distributing electrodes through direct coupling or electrostatic coupling between the rotary electrodes and the re spective distributing electrodes as the rotary electrodes rotates, thus impressing the signal voltage for forming an latent image upon each of said needle electrodes. In this way an electrostatic image of the needle electrodes which have been scanned by the rotary electrodes is formed on the recording medium which is moving across the tips of the recording electrodes. In this case it is necessary to rotate the rotary electrodes of the signal voltage distributor in synchronism with the input signal.

The latent image formed on the recording medium is then developed or visualized by a developing process utilizing a magnetic brush method, for example, and thereafter converted into a permanent image by any suitable fixing technique by means of heat fusing process or the like.

Generally in facsimiles and the like, the density of scanning lines of 4 lines per millimeter is required to obtain images of ordinary resolution, and most of the scanning width is of the order of 250 mm. Accordingly, it is necessary to use as many as 1,000 needle electrodes in the recording electrode member and hence 1,000 lead wires are required to connect these needle electrodes to the signal voltage distributor.

This results in substantial increase not only in the cost of material but also in the cost of fabrication. Moreover, it is impossible to make the recording device small and light in weight. Further, it. is extremely difficult to manufacture an electrode member for recording having a resolution of more than 4 lines per millimeter from the standpoint of manufacturing engineering. Moreover, the electrode member of electrostatic recording is very expensive and requires complicated fabrication steps because it comprises a plurality of needle electrodes embedded in an insulator made of synthetic resin. On the other hand, the magnetic brush method is commonly utilized at the means for developing latent images formed by said electrode member for recording to obtain visible powder images. In this method, a mixture of a carrier consisting of iron powder and a developing powder consisting of fine powder of a colored resin is utilized as the developing agent which is adapted to be attracted by a magnet to develop the latent image into a visible powder image. Since the developing powder alone is consumed during developing operation it is necessary to constantly supplement it so that the developing agent is always maintained in the best condition. However, since the developing powder comprising resin powder has a strong tendency to coagulate it is diflicult to continuously supplement it to a developing vessel at a small rate, so that, at present it is very diflicult to supplement under the best condition the developing powder to the developing Vessel.

Accordingly, it is the principal object of this invention to provide an improved multi-electrode type electrostatic recording device which is easy to manufacture, compact and light in weight and has an improved resolution.

Another object of this invention is to provide an improved multi-electrode type electrostatic recording device capable of greatly prolonging the useful life of the signal voltage distributing device and also increase the scanning speed.

A further object of this invention is to provide a novel multi-electrode type electrostatic recording device having a recording electrode element and a signal voltage distributing mechanism which are prepared by print wire technique.

A still further object of this invention is to provide an improved method of and apparatus for automatically supplementing a developing powder by which a small quantity of the developing powder adapted to develop a latent image into a visible powder image is continuously supplemented to the developing vessel.

Yet another object of this invention is to provide a novel method and apparatus for automatically supplementing developing powder by which the ratio of mixing a carrier and the developing powder in the developing agent is always maintained at the best condition.

Further objects and advantages of the invention will became apparent from the following detailed description of the invention when taken in connection with the accompanying drawings in which:

FIG. 1 is a plan view showing a base plate of a signal voltage distributor of an electrostatic recording device embodying this invention;

FIG. 2 shows a sectional view of one example of a recording electrode member of a multi-electrode type electrostatic recording device constructed according to the principle of this invention:

FIG. 3 is a side view, partly in section, of a modified electrode member for recording shown in FIG. 2;

FIG. 4 is a diagrammatic view showing the construction of one example of a developing member of an electrostatic recording device according to this invention; and

FIG. 5 is a diagrammatic view of a modified developing member shown in FIG. 4.

Referring now to the accompanying drawings, FIG. 1 thereof illustrates one example of a base plate of a signal distributor for use in an electrostatic recording device of this invention, in which the base plate 20 of a signal distributor comprises a laminated board 21 consisting of an electric insulator sheet with metal foils, copper foils for example, are bonded to the opposite sides thereof, a plurality of distributing segments 22a, 22b which are mounted on a circle at substantially the central portion of the laminated board 21, and a plurality of recording heads 23a, 23b of the same number as said segments 22a, 22b said recording heads being mounted in parallel along one edge of the laminated board 21.

These segments 22a, 22b and corresponding recording heads are interconnected by lead wires 24a, 24b. The segments 22a, 22b lead wires 24a, 24b

and recording heads 23a, 23b are formed by removing all portions of one of the copper foils except those comprising these elements by any suitable method such as the photoetching process, offset-printing process, chemical plating and the like.

Then, as shown in FIG. 2, a reenforcing plate 25 is mounted on the underside of the base plate 20 of the signal distributor and an electric conductive ring 29 is mounted by means of supporting posts 27 and 28 on the reenforcing plate 25 and another reenforcing plate 26 which is disposed on the recording head 23a. A shaft 30 for rotating an distributor arm is provided to extend through and journalled by the center of distributing segments 22a, 22b of the base plate 20 of the signal distributor. The central portion of the distributing arm 31 is secured to the rotary shaft 30 while the opposite ends of the arms 31 are provided with electric conducting brushes 32 and 33, one of the brushes 32 being disposed to slide on the electric conductive ring 29 whereas the other brush 33 to slide on the distributing segments 22a, 22b. In this case, the width of the distributing brush 33 as measured in the direction of rotation is made sufliciently smaller than the width of the distributing segments 22a, 22b. The reference numeral 34 represents an electrostatic recording sheet.

It is to be understood that the electrostatic recording sheet 35 is moved in direct contact with the recording surface of the recording heads 23a, 23b and is also moved in the direction perpendicular to the base plate 20 of the signal distributor as viewed in FIG. 1 and in the direction indicated by an arrow, as shown in FIG. 2. Then, the distributing arm 31 is rotated at a desired number of revolutions. An input picture signal voltage impressed upon the conductive supply ring 29 will thus be sequentially supplied to various distributing segments 22a, 22b through the electric conductive brush 32, through the distributing arm 31 and the electric conductive brush 33. The input picture signal voltage supplied to these seg ments 22a, 22b is then successively supplied to respective recording heads 23a, 23b via lead wires 24a, 24b

whereby the signal voltage is distributed on the electrostatic recording sheet from its left end to its right hand end to effect horizontal scanning and hence is recorded on the sheet. The electrostatic image thus recorded is developed or visualized into a visible powder image by means of a developing process to be described later.

Since the electrode member for recording is constructed as above described, the distributing mechanism and the recording heads are fabricated as a unitary structure which contributes to reduce dimensions and weight of the device and to substantially eliminate wiring work. Therefore, the recording device can be fabricated at low cost. By connecting to the ground the copper foil bonded to the rear surface of the base plate of the signal distributor, the

shielding effect for the recording heads is improved thus increasing the resolution of the record in the direction of horizontal scanning. Although in the prior art recording heads 4 lines per millimeter have been the maximum number that can be practically fabricated, according to this invention, this number can be increased to about 10 lines/ mm. thus greatly improving the resolution power.

The base plate of the signal distributor shown and described in the foregoing embodiment may be semicircular, if desired, and the electric conductive ring may be mounted at a position indicated by dotted lines 36 shown in FIG. 1.

FIG. 3 shows a modified electrode member for recording for use in the electrostatic recording device of this invention. In this modification a reenforcing plate 45 is secured to the lower surface of the base plate 20 of a signal distributor which is shown in FIG. 1 and a cathode ray tube 46 is secured on the upper surface of the base plate 20. In this embodiment, the cathode ray tube 46 is not provided with the usual fluorescent glass plate but the base plate 20 serves as a target, and there is provided a suitable deflecting system (not shown) to scan the distributing segments 22a, 22b with an electron beam emitted from an electron gun, not shown. A reenforcing plate 47 is mounted upon the upper surface of the recording heads 23a, 23b. The reference numeral 48 designates an electrostatic recording sheet.

The electrostatic recording sheet is held in direct contact with the recording surface of the recording heads 23a, 23b or is maintained to face to the recording surface with a suitable air gap. The recording sheet is moved in the direction of an arrow to effect vertical scanning. Then the vertical and horizontal deflectors of the deflecting system are adjusted to cause the electron beam emitted from the electron gun to scan in circular pattern and at a required speed to surfaces of distributor segments on the base plate 20 of the signal distributor. When the intensity of the electron beam emitted from the electron gun of the cathode ray tub 46 is modulated by the signal to be recorded an electric charge corresponding to the signal voltage to be recorded will be successively applied to the respective distributor segments 22a, 22b at the desired speed. The signal voltage to be recorded which has been distributed among distributor segments 22a, 22b in this manner will be sequentially supplied to respective recording heads 23a, 23b through lead wires 24a, 24b whereby the voltage is distributed on the electrostatic recording sheet 48 from its left hand end toward its right hand end thus effecting horizontal scanning and the signal voltage is recorded on the sheet. The recorded latent image will be visualized to form a visible powder image by the developing process to be described later.

In this embodiment having the construction as above described, electron beam scanning is substituted for the mechanical contact scanning of the first embodiment with the result that wear and friction are eliminated and the useful life of the device can be prolonged. Moreover, it is also possible to increase th scanning speed.

If shielding wires are formed between electrodes by a suitable etching process the resolution can be further improved.

The electrostatic latent image which was recorded on the recording sheet 34 or 48 will then be developed or visualized to form a satisfactory visible image by means of a developing device shown in FIG. 4. More particularly, a developing agent 51 consisting of a mixture of a suitable quantity of a carrier comprising iron powder and a developing powder comprising a colored resin powder is contained in a developing vessel 52. A adjacent to this vessel 52 is disposed a developing powder supple mentary vessel 53 which contains supplementary developing agent 54 consisting of a mixtur of the developing powder and iron powder carrier, said mixture containing the former at a higher percentage than the latter. Both vessels 52 and 53 are opened at their upper portions and a metal roller 55 is positioned above the adjoining edges of these vessels, said roller being rotated such that its lower surface rotates from the vessel 53 to the vessel 52, or in the clockwise direction as viewed in FIG. 1. Magnetic brushes rotating about axes 56 and 57 are mounted respectively in the developing vessel 52 and the developing powder supplementary vessel 53, said magnetic brushes being so constructed and arranged that their poles are intermittently brought close to the metal roller 55.

A DC. voltage from a DC. source 61 is applied to the metal roller through a voltage adjuster 60 which is operated in synchronism with the rotation of the magnetic brush 58 in the developing vessel 52 in such a manner that it will interrupt the voltage or decrease the voltage to a very low value when the magnetic pole of the magnetic brush 58 is rotated to a position close to the metal roller 55.

With this arrangement, by the rotation of the magnetic brush 59 in the developing powder supplementary vessel 53 the supplementary developingagent 54 is conveyed onto the metal roller 55. In this case the carrier and developing powder are electrostatically charged to opposite polarities by the agitation caused by the rotary magnetic brush 59. The polarties of these'charges are dependent upon the material of the developing powder. For example, it is assumed now that the polarity of the charge of the developing powder is positive and that of the iron powder carrier is negative, then a negative voltage will be impressed upon the metal roller 55 from the DC. source 61 by; manipulating the voltage adjuster 60.

As a result, when the magnetic brush 59 comes to contact with the peripheral surface of the metal roller 55 the positively charged developing powder of the developing agent 54 which is attracted by and secured on the pole of the magnetic brush 59 is transferred onto the outer periphery of the metal roll 55 and is then conveyed'towards the developing vessel 52 as the roll rotates. As has been pointed out hereinabove, when the magnetic pole of the magnetic brush 58 rotating in th developing vessel 52 is brought into contact with the outer periphcry of the metal roller 55, the voltage applied to the roller is interrupted or reduced to an extremely low value to decrease the attractive force for th developing powder. Since the carrier of the magnetic brush 58 is charged negatively, the developing powder which has been attracted by the periphery of the metal roller 55 is now attracted by the magnetic brush 58 and is then supplemented into the developing vessel 52.

With this construction it is possible to continuously and at a uniform rate, supplement into the developing vessel the developing powder which ha a tendency to coagulate. Moreover, the quantity supplemented can be readily and accurately controlled by adjusting the biassing potential applied to the metal roller. Therefore, when latent images are developed by the disclosed developing device, the images can be converted into visible powder images, always under the best conditon. Thus, the novel developing device is especially suitable for continuously developing a number of electrostatic latent images as in an electrostatic facsimile picture. receiving apparatus, for example.

FIG. 5 illustrates a modified embodiment of the developing device comprising a developing agent container or vessel 72 containing a developing agent 71 consisting of a mixture of an iron powder carrier and a suitable amount of developing powder and a developing agent supplementary vessel 73 positioned adjacent to the vessel 72. Again the top portions of vessels 72 and 73 are open and the supplementary developing agent 74 contained in the vessel 73 contains higher proportion of developing powder than that of the carrier. Above the adjoining portions of the vessels 72 and 73 is situated a metal roller 75 with its peripheral surface covered by an insulating coating, which is rotated such that that its lower surface moves from the supplementary vessel 73 towards the developing vessel 72. Within the supplementary vessel 73 is mounted a rotary magnetic brush 76 which serves to stir the supplementing developing agent 74 contained therein and is rotated such that its pole is brought into sliding engagement with the periphery of the metal roller. Above the developing vessel 72 is disposed a scraper 78 for the developing powder which is hinged at one end and biased to engage the peripheral surface of the roller 75 by means of a spring 77. As shown, a DO. bias voltage is impressed upon the metal roller from a DC. source 79.

In operation as the supplementary developing agent 74 is stirred by the magnetic brush 76, the carrier and the developing powder are charged with electrostatic charges of opposite polarities. If it is supposed now that the carrier is charged negatively, while the developing powder positively, the metal roller 75 is to be supplied with negative bias voltage from the DC. source 79.

Upon rotation of the magnetic brush 76, its pole will carry the positively charged developing powder which is being attracted by it to the metal roller 75. Since, in this case, the metal roller 75 is impressed with a negative biasing voltage as above mentioned, the positively charged developing powder will be attracted by and transferred onto the peripheral surface of the rotating metal roll when the pole of the magnetic brush 76 is brought into sliding engagement with the roller 75, and the developing powder is then conveyed towards the developing vessel 72 as the roller rotates. The developing powder is then removed from the roller 75 by the action of the scraper 78 and falls into the developing vessel as a supplementary developing powder.

In order to prevent permanent sticking of the developing powder to the scraper 78, it is advantageous to impart suitable external vibration to the scraper 78 or to impart up and down motions to the scraper by means of a cam ratchet mechanism and the like thus preventing coagulation of the adhered developing powder.

Alternatively, the scraper 78 may be moved vertically by providing a number of slots on the outer periphery of the metal roller 75 in parallel with the axis of the roller. While in the above described embodiments the developing powder was attracted by the metal roller 75 by applying a biasing voltage thereto, the powder can also be attracted by a static charge formed on the roller by friction. Further, the means for conveying the developing powder is not limited to metal roller but a conveyor belt travelling from the developing powder supplemental vessel to the developing vessel can also be utilized.

With this construction, it is possible to automatically and continuously supplement a small quantity of the developing powder having a tendency to coagulate into the developing vessel. Moreover, the quantity supplemented can be readily adjusted by varying the magnitude of the voltage applied to the developing powder conveyor or the magnitude of the electrostatic charge created by friction. Thus, like the first embodiment this modification is also suitable for continuously developing a number of latent images.

What is claimed is:

1. A developing device for an electrostatic recording apparatus, comprising:

a developing vessel which contains a developing agent consisting of a developing powder and a carrier;

a supplementary vessel which contains a supplementary developing agent consisting of the developing powder and the carrier and containing the former at a higher percentage than the latter;

a rotatable magnetic brush mounted in said supplementary vessel and for stirring the supplementary developing agent to charge the supplementary developing powder and the carrier to have opposite polarities, said magnetic brush also attracting the supplementary powder and the carrier;

conveying means slidably engageable by said brush and located above said developing vessel for conveying said supplementary developing powder from said supplementary vessel to said developing vessel;

a voltage source connected to said conveying means and supplying thereto a voltage having a polarity oppositeto that of the charge of the supplementary developing powder, said voltage serving to attract the supplementary developing powder onto said conveying means; and

scraping means adapted to be brought in contact with said conveying means for removing said supplementary developing powder from said conveying means, said removed powder falling into said developing vessel to supplement said developing powder.

2. The developing device according to claim 1, wherein said conveying means comprises a rotatable metal roller.

3. The developing device according to claim 2, wherein said scraping means comprises a rotatable magnetic brush.

4. The developing device according to claim 3, further comprising a voltage adjuster operated in synchronism with the rotation of said scraping magnetic brush such that when the pole of said scraping brush is rotated to a position close to said metal roller, said adjuster causes the voltage supplied to said metal roller to decrease to a low value which is insuflicient for said metal roller to hold the supplementary developing powder.

5. The developing device according to claim 2, wherein said scraping means comprises:

a scraper hinged at one end; and

means biasing said scraper for engagement with the periphery of said metal roller.

References Cited UNITED STATES PATENTS PETER FELDMAN, Primary Examiner US. Cl. X.R. 

